JP2019085877A - Ignition device for internal combustion engine - Google Patents

Abstract

To provide an ignition device for an internal combustion engine which can prevent an electric potential rise in the inside of an alternating current power supply even if ignition action only by a direct-current power supply is continued regenerative power by a discharging current of a capacitor is accumulated.SOLUTION: In an ignition device for an internal combustion engine having an ignition plug, a discharging power supply, and a high-frequency alternating power supply, the high frequency alternating current power supply is provided with a direct current voltage source; an input capacitor; a voltage detecting means for detecting the application voltage of the input capacitor; an inverter which converts the direct current voltage outputted from the direct current voltage source into alternating current voltage; a transformer which connects a primary coil to an output end of the inverter; a resonance circuit which resonates the alternating voltage outputted from the inverter; a current detecting means which detects a current supplied from the high frequency alternating current power supply to the ignition pug; and a control portion which controls the switching element configuring the inverter.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an ignition device for an internal combustion engine utilizing high frequency plasma discharge.

  An exhaust gas recirculation system (EGR: Exhaust Gas Recirculation) for introducing part of lean fuel gas and exhaust gas to the intake side and re-inhales as a method of improving fuel efficiency of internal combustion engines such as automobile engines etc., and increasing compression ratio of combustion chamber Etc. are used. However, in all methods, steady ignition is a problem, and it was necessary to improve the ignitability. As a general ignition device for an internal combustion engine, a device that generates a high voltage by a DC power source configured by an ignition coil and an igniter and generates a breakdown discharge between electrodes of a spark plug is used.

On the other hand, a plasma igniter has been proposed as one of internal combustion engine igniters that improves the ignitability. The plasma igniter includes a spark plug, a DC power supply, an AC power supply, a mixing unit, and an ignition control unit. Then, by generating an alternating current plasma between the center electrode and the ground electrode in the spark plug, ignition is performed, and thereafter the alternating current power supplied to the spark plug is reduced to improve the life of the spark plug.
(For example, refer to patent document 1)

  Also, a high frequency plasma ignition device has been proposed as one example of circuit configuration of an alternating current power supply. This is composed of a battery, a full bridge inverter, a transformer, a resonant circuit, a spark plug, and a high voltage circuit, and the arms of the inverter circuit are made common to make the number of arms smaller than twice the number of spark plugs. The (For example, refer to patent document 2)

Unexamined-Japanese-Patent No. 2012-112310 (third-page 13, FIGS. 1-2) JP, 2015-86702, A (page 2-page 10, FIG. 1)

  However, in the plasma ignition device proposed in Patent Document 1, the transmission path of the high voltage output from the DC power supply and the transmission path of the high frequency AC voltage output from the AC power supply are one transmission path. Collectively connected to the spark plug. The AC power supply is separated from the high voltage output by the DC power supply at the ignition timing by the condenser of the mixing unit. In the plasma igniter configured as described above, the dielectric breakdown in the combustion chamber is caused by the voltage between the electrodes of the spark plug reaching the discharge start voltage, and the capacitor of the mixing section also has the same voltage between the electrodes of the spark plug. A voltage is applied. The charge stored in the capacitor has the problem of flowing into the AC power supply as a discharge current at the same time as dielectric breakdown occurs.

  On the other hand, in the high frequency plasma ignition device proposed in Patent Document 2, the discharge current is rectified by the diode of the switching element of the inverter and regenerated to the battery. However, depending on the operating conditions of the internal combustion engine, there are also conditions under which fuel gas can be easily ignited, and in order to suppress power consumption by the igniter at this time, the AC power supply is stopped and the ignition operation is performed only by the DC power supply. . When the ignition operation using only the DC power supply continues, the discharge current flows into the AC power supply every time the ignition is performed, and is accumulated as regenerative power. Although the regenerative power is accumulated but the AC power supply does not operate, the regenerative power can not be consumed, and the potential inside the AC power supply rises. Therefore, it is necessary to configure the AC power supply with high-voltage circuit elements, and there is a limit to the miniaturization of the AC power supply.

  The present invention has been made to solve the above-mentioned problems, and the ignition operation using only the DC power supply continues, and the voltage applied inside the AC power supply rises even if regenerative power is accumulated due to the discharge current of the capacitor. It is an object of the present invention to provide an ignition device for an internal combustion engine that can prevent the

In the ignition device for an internal combustion engine according to the present invention, a high DC voltage is applied between an electrode of the ignition plug and an ignition plug for igniting a combustible mixture in a combustion chamber of the internal combustion engine to generate spark discharge between the electrodes. In an igniter for an internal combustion engine, comprising: a discharge power source; and a high frequency AC power source for applying a high frequency voltage to a discharge path of the spark discharge to generate a high frequency plasma between the electrodes;
The high frequency alternating current power supply includes a direct current voltage source, an input capacitor, voltage detecting means for detecting an applied voltage of the input capacitor, and a plurality of switching elements, and the direct current voltage output from the direct current voltage source is an alternating voltage , A transformer having a primary side winding connected to the output end of the inverter, and a secondary side winding of the transformer, having at least one or more capacitors and a reactor, and an output from the inverter Circuit for resonating the alternating current voltage, current detection means for detecting the current supplied from the high frequency alternating current power supply to the spark plug, and a control unit for controlling the on / off operation of the switching element constituting the inverter And
The control unit operates the inverter to consume energy stored in the input capacitor as an energy consumption operation when the detected voltage of the input capacitor is higher than a preset threshold voltage. It is a feature.

  According to the igniter for an internal combustion engine according to the present invention, the ignition operation by only the discharge power supply continues, and even if the regenerative power by the discharge current of the resonance capacitor is accumulated in the high frequency AC power supply, It is possible to prevent the rise.

FIG. 1 is a diagram showing an example of a circuit configuration of an internal combustion engine ignition device according to Embodiment 1 of the present invention. It is a figure which shows the ignition timing of the internal combustion engine ignition device concerning Embodiment 1 of this invention. It is a figure which shows the inverter operation | movement of the high frequency alternating current power supply of the ignition device for internal combustion engines concerning Embodiment 1 of this invention. It is a figure which shows the characteristic of the resonance load of the internal combustion engine ignition device concerning Embodiment 1 of this invention. It is a figure which shows the timing chart of energy consumption operation | movement of the ignition device for internal combustion engines concerning Embodiment 1 of this invention. It is a figure which shows the circuit structural example of the internal combustion engine ignition device concerning Embodiment 3 of this invention. It is a figure which shows the reignition operation | movement of the internal combustion engine ignition device concerning Embodiment 3 of this invention.

Embodiment 1
First, the configuration of the internal combustion engine ignition device according to the first embodiment of the present invention will be described. FIG. 1 is a diagram showing a circuit configuration example of an internal combustion engine ignition device according to a first embodiment of the present invention.

  The internal combustion engine ignition device 1 has an ignition plug 10, a discharge power supply 11, and a high frequency AC power supply 2.

  The discharge power source 11 applies a high DC voltage to cause dielectric breakdown between the electrodes of the spark plug 10. A spark discharge can be generated between the electrodes by applying a high DC voltage between the electrodes of the spark plug. The spark plug 10 ignites the combustible mixture in the combustion chamber of the internal combustion engine.

  The high frequency AC power supply 2 applies a high frequency voltage to the spark plug 10. A high frequency plasma can be generated between the electrodes by applying a high frequency voltage to the discharge path of the spark discharge. The high frequency AC power supply 2 includes a DC voltage source 3, an input capacitor 4, a voltage detection means 8, an inverter 5, a transformer 6, a resonance circuit 7, and a current detection means 9 for detecting a current output from the high frequency AC power supply 2 to the spark plug 10. , And a control unit 12. The direct current voltage source 3 is constituted of, for example, a battery mounted on a vehicle. The voltage detection means 8 detects the voltage applied to the input capacitor 4.

  The input capacitor 4 is provided between the DC voltage source 3 and the inverter 5 in the circuit configuration to suppress the ripple voltage from the DC voltage source 3.

  The inverter 5 has a plurality of switching elements 51, 52, 53, 54, and converts the DC voltage output from the DC voltage source 3 into an AC voltage. In the present embodiment, a DC voltage is converted to an AC voltage through the input capacitor 4.

  The inverter 5 is composed of a first leg consisting of a series circuit of switching elements 51 and 52 and a second leg consisting of a series circuit of switching elements 53 and 54. The drain ends of the switching elements 51 and 53 of the inverter 5 are connected to the DC voltage source 3 and the positive end of the input capacitor 4. The source terminals of the switching elements 52 and 54 of the inverter 5 are connected to the DC voltage source 3 and the negative terminal of the input capacitor 4. Each of the switching elements 51 to 54 has an antiparallel diode (body diode).

  In the present embodiment, the circuit configuration of the inverter 5 will be described taking a full bridge circuit as an example, but another configuration such as a half bridge circuit may be used, for example. Although each switching element has a MOS (Metal Oxide Semiconductor) configuration including a diode, it may be another semiconductor element such as an IGBT (Insulated Gate Bipolar Transistor), for example.

  The transformer 6 boosts the alternating voltage output from the inverter 5. The transformer 6 has a primary winding 61 and a secondary winding 62. The primary side winding 61 is connected to the output end of the inverter 5, and the secondary side winding 62 is connected to the resonant circuit 7.

  The turns ratio of the primary winding 61 and the secondary winding 62 of the transformer 6 is 1: n. In order to boost the voltage on the secondary side winding 62 side of the transformer 6 to a high voltage, n is a real number greater than one. Thus, the voltage generated between the secondary windings 62 of the transformer 6 is converted to n times the voltage generated between the primary windings 61 of the transformer 6. Therefore, the current flowing through the secondary winding 62 of the transformer 6 is converted to 1 / n times the current flowing through the primary winding 61 of the transformer 6.

  The resonant circuit 7 is connected to the secondary side winding 62 of the transformer 6 and has one resonant capacitor 72 and one resonant reactor 71. The resonant circuit 7 shapes the alternating voltage output from the inverter 5 into a sine wave. As an example of the resonant circuit 7, a series LC circuit is used in the present embodiment, and specifically, the secondary side winding 62 of the transformer 6, the resonant reactor 71, and the resonant capacitor 72 are connected in series in order . Needless to say, the same ignition operation can be performed even if another resonant circuit is applied. Further, in the present embodiment, one resonance capacitor 72 and one resonance reactor 71 are provided. However, as long as at least one resonance capacitor 72 and at least one resonance reactor 71 are provided, plural resonance capacitors may be provided.

  The control unit 12 controls the on / off operation of each switching element 51, 52, 53, 54 in the inverter 5. This control consumes the energy stored in the input capacitor 4 as an energy consumption operation when the voltage applied to the input capacitor 4 is higher than a preset threshold voltage, so that the switching elements 51 and 52 of the inverter 5 are used. , 53, 54 are operated.

  Next, the basic operation of the internal combustion engine ignition device 1 in the present embodiment will be described. FIG. 2 is a diagram showing a timing chart of high frequency plasma ignition in the first embodiment of the present invention.

  FIG. 2 shows the states of the ignition timing signal, the inverter drive signal, the spark plug voltage, the spark plug current, and the input capacitor applied voltage. Each of T1 to T3 in the figure indicates a certain time.

  At time T1 in FIG. 2, the ignition device 1 for an internal combustion engine receives an ignition plug from the discharge power supply 11 in response to the falling of the ignition timing signal output from an engine control unit (hereinafter referred to as ECU) not shown. Start applying negative voltage to 10.

  Time T2 in FIG. 2 is the time when the voltage applied to the spark plug 10 reaches a certain voltage. At time T2, the electrodes of the spark plug 10 are broken down and spark discharge occurs. The voltage at which the spark plug 10 reaches dielectric breakdown varies depending on the distance between the electrodes of the spark plug 10 and the state of the combustion chamber, but it is necessary to apply several kV to several tens kV.

  After the spark plug 10 is broken down, at time T3 in FIG. 2, the operation of the high frequency AC power supply 2 is started, and the DC voltage applied to the input capacitor 4 is output by the inverter 5 as a high frequency AC voltage.

  The high frequency AC voltage output from the inverter 5 is boosted by the transformer 6. The alternating voltage boosted by the transformer 6 is shaped into a sine wave by the resonant circuit 7 and applied to the spark plug 10 as a high frequency alternating voltage of several MHz having a voltage value of several hundred volts to several kilovolts. Then, high frequency plasma ignition is performed on a mixture of fuel and air in the combustion chamber of the internal combustion engine.

  Next, an operation waveform of the inverter 5 when the high frequency AC power supply 2 is performing the high frequency plasma ignition operation will be described with reference to FIG. Here, the output voltage of the inverter 5 is positive when the potential at the connection point between the switching elements 51 and 52 in the first leg is higher than the potential at the connection point between the switching elements 53 and 54 in the second leg. The direction of the inverter 5 output current flows from the connection point of the switching elements 51 and 52 of the first leg to the connection point of the switching elements 53 and 54 of the second leg via the primary winding 61 of the transformer 6 as positive.

  FIG. 3A shows a waveform in which the output current of the inverter 5 is delayed in phase with respect to the output voltage of the inverter 5. (B) of FIG. 3 shows a waveform in which the output current of the inverter is in the lead phase with respect to the output voltage of the inverter 5. The condition in which the output current of the inverter 5 is delayed in phase with respect to the output voltage of the inverter 5 is when the combined reactance formed by the resonance circuit 7 and the spark plug 10 is inductive. However, when dielectric breakdown occurs between the electrodes of the spark plug 10 to form a discharge path, the spark plug 10 is regarded as a resistance component, and therefore only the combined reluctance of the resonant circuit 7 may be considered.

  FIG. 3A will be described in detail. Time Ta in FIG. 3A indicates the timing at which the gate signals of the switching elements 51 and 54 rise. Time Tb represents the timing at which the gate signals of the switching elements 52 and 53 rise.

  At time Ta when the gate signals of the switching elements 51 and 54 rise, a negative current flows in the switching elements 51 and 54. This means that the antiparallel diodes of the switching elements 51 and 54 are conducting, and the drain-source voltage of the switching elements 51 and 54 to be turned on becomes zero. Therefore, zero voltage switching is established in switching elements 51 and 54, and switching loss at turn-on can be reduced. The same applies to the time Tb when the switching elements 52 and 53 whose polarity of switching is reversed are turned on.

  FIG. 3B will be described in detail. At time Tc when the gate signals of the switching elements 51 and 54 rise, the switching elements 51 and 54 become conductive, and the inverter 5 outputs a positive current.

  At time Td, the polarity of the inverter output current is inverted. At this time, the switching elements 51 and 54 are conductive. Therefore, current flows from the source to the drain of the switching elements 51 and 54.

  The switching elements 51 and 54 are turned off at time Te. As a result, current flows in the antiparallel diodes of the switching elements 51 and 54, and the input capacitor 4 is regenerated.

  Next, at time Tf, the switching elements 52 and 53 are turned on. At this time, since no current flows in the switching elements 52 and 53, the switching elements 52 and 53 become hard switching.

  At the same time as switching elements 52 and 53 become conductive, recovery of anti-parallel diodes of switching elements 51 and 54 occurs. Since both of the switching elements 51 and 52 of the first leg become conductive during the recovery period, a short circuit occurs in the first leg, and a large current instantaneously flows through the first leg. In the switching elements 51 and 52, a loss due to the short circuit current occurs, and heat generation of the switching element increases. Therefore, it is necessary to strengthen the change to the switching element having a characteristic that can withstand the short circuit current and the cooling capability.

  From the above, in the inverter 5, the output current of the inverter 5 is delayed in phase with respect to the output voltage of the inverter 5, that is, the resonant load circuit including the resonant circuit 7 and the spark plug 10 is operated in a frequency range where inductive reactance is generated. I assume.

  Next, the relationship between the resonance point of the resonance reactor 71 and the resonance capacitor 72 in the resonance circuit 7 and the resonance gain will be described. FIG. 4 is a diagram showing the relationship between the resonance point of the load including the resonance reactor 71 and the resonance capacitor 72 and the resonance gain.

  The vertical axis in FIG. 4 indicates the gain, and the horizontal axis indicates the frequency. In FIG. 4, in the frequency region higher than the resonance point, when the frequency is increased, the resonance gain is reduced and the output of the high frequency AC power supply is reduced. Further, in the frequency region lower than the resonance point, when the frequency is increased, the resonance gain is increased and the output of the high frequency AC power supply is increased. That is, the combined reactance of the resonant circuit is inductive for the inverter 5 at frequencies higher than the resonance point, and capacitive at frequencies lower than the resonance point.

  In the inverter 5 according to the present embodiment, as described above, the output current has a delay phase with respect to the output voltage of the inverter 5 in order to perform zero voltage switching when the switching elements 51 and 54 of the inverter 5 are turned on. It is working. Therefore, in the present embodiment, the inverter 5 is operated in a frequency range where the switching frequency of the switching element is higher than the resonance point, that is, in a frequency range where the combined reactance of the resonant circuit 7 becomes inductive.

  By adjusting the switching frequency of the inverter 5 to change the resonance gain, the voltage applied to the spark plug 10 can be changed to control the current flowing through the spark plug 10. Specifically, when the detected current detected by the current detection means 9 is lower than the current request value of the spark plug 10, the frequency is adjusted to lower the switching frequency so as to approach the resonance point. Also, when the detected current is higher than the current demand value of the spark plug, adjustment is performed to increase the switching frequency. By adjusting the switching frequency in this manner, control of the current flowing through the spark plug 10 becomes possible.

  The energy consumption operation of the internal combustion engine ignition device 1 according to the present embodiment will be described using FIGS. 2 and 5.

  The internal combustion engine ignition device 1 repeats the above-described ignition operation at each ignition timing. In the ignition operation, when dielectric breakdown occurs between the electrodes of the spark plug 10 by the discharge power supply 11, a voltage equal to the inter-electrode voltage of the spark plug 10 is applied to the resonant capacitor 72 constituting the resonant circuit 7. . The energy stored in the resonant capacitor 72 is discharged as a discharge current oscillating at a resonant frequency generated by the resonant reactor 71 and the resonant capacitor 72 simultaneously with the dielectric breakdown between the electrodes of the spark plug 10 shown at time T2 in FIG. .

  The discharge current flows into the inverter 5 through the transformer 6. At this time, the inverter 5 is not operating, and is rectified by the anti-parallel diodes of the switching elements 51 to 54 and regenerated to the input capacitor 4. The voltage applied to the input capacitor 4 rises with the regenerated power consisting of the discharge current.

  Thereafter, at time T3, the high frequency plasma ignition operation starts, and the energy of the input capacitor 4 is consumed by the operation of the inverter 5, and the voltage applied to the input capacitor 4 decreases. As described above, when the voltage applied to the input capacitor is lower than the output voltage of the DC voltage source, it is charged by the DC voltage source and becomes the same potential.

  When the high frequency plasma ignition is performed, the above-described series of operations are repeated, but depending on the operating state of the internal combustion engine, ignition may be performed only by spark ignition by the discharge power supply 11. When the ignition operation by only the discharge power supply 11 is repeated, the input capacitor 4 of the high frequency AC power supply 2 is repeatedly charged with regenerative power by the discharge current of the resonance capacitor 72. At this time, since the high frequency plasma ignition operation by the operation of the inverter 5 is not performed, the energy of the input capacitor 4 is not consumed, and the applied voltage gradually increases. In order to allow the increase of the applied voltage, a high breakdown voltage circuit element is required, and in that case, there is a limit to the miniaturization of the AC power supply.

  Therefore, in the present embodiment, in the case where the ignition operation of only the above-described discharge power supply 11 is repeated, the following operation is performed in order to avoid a rise in the voltage applied to the input capacitor 4.

  FIG. 5 is a diagram showing a timing chart of the energy consumption operation. The figure shows the operating state of the ignition timing signal, the inverter drive signal, the spark plug voltage, the spark plug current, and the input capacitor applied voltage.

  As an operation method for avoiding a rise in the voltage applied to the input capacitor 4, in the present embodiment, the voltage detection means 8 monitors the voltage applied to the input capacitor 4. Then, the magnitude is compared with a preset threshold voltage. In the present embodiment, the threshold voltage is equal to or higher than the output voltage of the DC voltage source 3 and lower than the rated voltage of the circuit elements constituting the high frequency AC power supply 2.

  By comparison, when the voltage detection means 8 detects the applied voltage of the input capacitor 4 having a threshold voltage or more, the control unit 12 ends the insulation breakdown between the electrodes of the spark plug 10 by the discharge power supply 11 and returns to the insulation state , And outputs an operation signal to the inverter 5. The operation of the inverter 5 at this time performs the same switching operation as when performing the normal high frequency plasma ignition, and energy stored in the input capacitor 4 with the loss generated from the circuit element constituting the high frequency AC power supply 2 To consume

  When the voltage applied to the input capacitor 4 decreases due to the energy consumption operation of the inverter 5 described above, and the next ignition timing signal is output, or when the detected voltage decreases to the same potential as the DC voltage source 3, the inverter 5 Stop the energy consumption operation.

  Since the output voltage of the high frequency AC power supply 2 is less than the dielectric breakdown voltage between the electrodes of the spark plug 10, the capacitive component between the electrodes is regarded as a load. Therefore, two series of the capacity component of the resonance capacitor 72 and the spark plug 10 become a combined capacity, and the combined capacity is smaller than the capacity of the resonance capacitor 72. Therefore, the resonance point of the load circuit in the energy consumption operation is shifted to a higher frequency side than the resonance point of the load circuit in the high frequency plasma ignition operation.

  The switching frequency in high frequency plasma ignition operation and the switching frequency in energy consumption operation are made the same. In this case, depending on the configuration of the resonance circuit 7, it is conceivable that the switching frequency of the inverter 5 overlaps the frequency region or the resonance point where the capacity becomes capacitive during the energy consumption operation. However, since the output voltage of the high frequency AC power supply 2 is a voltage sufficiently lower than the dielectric breakdown voltage of the spark plug 10, the discharge is not performed.

  When it is desired to avoid that the switching frequency of the inverter 5 overlaps the capacitive frequency or the resonance point during the energy consumption operation, the resonance point of the resonant load circuit when the spark plug 10 is broken down, and the ignition The resonance point of the resonant load circuit when the plug 10 is not broken down is confirmed in advance. Then, the switching frequency of the inverter 5 in the energy consumption operation may be operated so as to be higher than the resonance point formed by the resonance circuit and the stray capacitance component of the spark plug 10.

  As described above, when the detected voltage of the input capacitor 4 becomes higher than a preset threshold voltage, the ignition device 1 for an internal combustion engine of the present embodiment stores energy stored in the input capacitor 4 as an energy consumption operation. The inverter 5 is operated to consume the

  Therefore, even if the ignition operation by only the discharge power supply 11 is repeated, the regenerative energy stored in the input capacitor 4 can be appropriately consumed. As a result, it is possible to prevent a rise in the applied voltage of the high frequency AC power supply 2.

Second Embodiment
The second embodiment is different in the configuration in which the energy consumption operation of the first embodiment is performed even in a period in which the electrodes of the spark plug 10 are in dielectric breakdown. In the second embodiment, parts different from the first embodiment of the present invention will be described, and description of the same or corresponding parts will be omitted.

  The energy consumption operation in the first embodiment is limited to be performed after the breakdown between the electrodes of the spark plug 10 is completed. This is because the high frequency AC power supply 2 outputs a voltage higher than the voltage required for high frequency plasma discharge. At this time, if the high frequency AC power supply 2 operates when the electrodes of the spark plug 10 are broken down, high frequency plasma discharge is performed, and depending on the operating state of the internal combustion engine, unnecessary ignition occurs. This ignition operation leads to energy consumption of the battery serving as the DC voltage source 3 and mechanical stress to the internal combustion engine.

  Therefore, in the second embodiment, the duty ratio of the on-pulses of the switching elements 51 to 54 of the inverter 5 is reduced when the energy consumption operation is performed. By reducing the on time of the switching elements 51 to 54, the excitation time of the transformer 6 is reduced, and the peak value of the output voltage and output current of the high frequency AC power supply 2 is reduced.

  By setting the output voltage of the high frequency AC power supply 2 to less than the discharge maintaining voltage required for high frequency plasma ignition in this operation, energy consumption operation is performed without high frequency plasma discharge even if the electrodes between the electrodes of the spark plug 10 are broken down. It can be performed.

  Thus, the above-described energy operation eliminates the restriction on the timing of performing the energy consumption operation. As a result, after the voltage detection means 8 detects that the voltage applied to the input capacitor 4 is equal to or higher than the threshold voltage, it is possible to carry out the energy consumption operation immediately.

  Therefore, in the second embodiment, as in the first embodiment, in addition to the effect that the regenerative energy stored in the input capacitor 4 can be appropriately consumed, the consumption operation can be implemented immediately. Therefore, the rise of the applied voltage of the high frequency alternating current power supply 2 can be prevented.

Third Embodiment
FIG. 6 is a view showing an ignition device for an internal combustion engine according to a third embodiment of the present invention. 6, the same reference numerals as those in FIG. 1 denote the same or corresponding components as those in FIG. 1, and the description thereof will be omitted. The configuration in which the diode bridge circuit 13 is connected between the inverter 5 and the transformer 6 in the high frequency AC power supply 2 is different from the first embodiment and the second embodiment of the present invention.

  In the third embodiment of the present invention, portions different from the first and second embodiments of the present invention will be described, and the description of the same or corresponding portions will be omitted. The configuration of the high frequency AC power supply 2 of the internal combustion engine ignition device 1 according to the third embodiment will be described with reference to FIG.

  The high frequency AC power supply 2 outputs the current output from the DC voltage source 3, the input capacitor 4, the voltage detection means 8, the inverter 5, the transformer 6, the resonance circuit 7 and the high frequency AC power supply 2 to the spark plug 10. It comprises a current detection means 9 for detecting and a control unit 12. Furthermore, the present embodiment has a diode bridge circuit 13 between the inverter 5 and the transformer 6.

  The diode bridge circuit 13 is composed of four diodes 131, 132, 133 and 134. The cathodes of the diodes 131 and 133 are connected to the drain ends of the switching elements 51 and 53 of the inverter 5, the DC voltage source 3 and the positive end of the input capacitor 4. The anodes of the diodes 132 and 134 are connected to the source terminals of the switching elements 52 and 54 of the inverter 5, the DC voltage source 3 and the negative terminal of the input capacitor 4.

  The connection point of the anode of the diode 131 and the cathode of the diode 132 is connected to one end 61 a of the transformer 6 primary side winding. The connection point of the anode of the diode 133 of the second leg and the cathode of the diode 134 is connected to the other end 61 b of the transformer 6 primary side winding. That is, the series circuit of the diode 131 and the diode 132 is a first leg, and the series circuit of the diode 133 and the diode 134 is a second leg.

  A misfire during the ignition operation will be described. The internal combustion engine ignition device 1 performs an ignition operation based on an ignition timing signal from the ECU. However, the condition of the combustion chamber or the wear of the electrode of the spark plug 10 may cause the spark formed between the electrodes of the spark plug 10 to misfire.

  When the spark is misfired, inductive energy remaining in the ignition coil of the discharge power source 11 is supplied between the electrodes of the spark plug 10, and ignition by dielectric breakdown is performed again. This ignition operation is hereinafter referred to as reignition.

  Reignition is performed out of synchronization with the ignition timing signal transmitted from the ECU. For this reason, even if the high frequency AC power supply 2 is in operation, reignition is performed when a misfire occurs. Further, since reignition causes insulation breakdown between the electrodes of the spark plug 10, a discharge current due to the resonance capacitor 72 is generated as in the insulation breakdown due to the ignition timing signal.

  Here, the case where reignition occurs while the high frequency AC power supply 2 without the diode bridge circuit 13 is in operation, and the discharge current from the resonance capacitor 72 flows into the inverter 5 will be described.

  For example, when the relationship between the switching phase of the inverter 5 and the phase of the discharge current becomes the leading phase as shown in FIG. 3B described above, the anti-parallel diodes of the switching elements are as described in the first embodiment. Recovery occurs and it is easy to short circuit. The length of the recovery period tends to depend on the blocking current.

  Since the discharge current output from the resonance capacitor 72 is twice the turns ratio of the transformer 6, the current to be cut off is longer than the recovery period generated in the high frequency plasma ignition operation. When the short circuit period becomes long, the transient heat generation due to the short circuit current becomes excessive, and the heat resistance temperature of the components of the high frequency AC power supply 2 is exceeded and the damage occurs. Alternatively, the high frequency AC power supply 2 frequently stops operating because the threshold of the temperature sensor (not shown) is exceeded.

  FIG. 7 is a view showing the reignition operation of the internal combustion engine ignition device 1. FIG. 7 shows the operating states of the ignition timing signal, the inverter drive signal, the spark plug voltage, and the spark plug current. Further, T1 to T5 in the figure indicate a certain time.

  The operation in the case of the configuration having the diode bridge circuit 13 of the third embodiment in the state of reignition will be described.

  When the diode bridge circuit 13 is connected between the inverter 5 and the transformer 6, the discharge current is shunted to the inverter 5 and the diode bridge circuit 13. Thus, the discharge current can be rectified regardless of the phase of the discharge current generated from the input capacitor 4 at the time of reignition. Therefore, it is possible to suppress the recovery loss and the recovery short circuit period that occur in the anti-parallel diodes of the switching elements of the inverter 5.

  Further, by setting the forward voltage characteristic of the diode used in the diode bridge circuit 13 to a voltage lower than that of the anti-parallel diode of the inverter 5, the rectified current of the diode bridge circuit 13 can be further increased. .

  Furthermore, the connection from the transformer 6 to the diode bridge circuit 13 is configured to be the shortest. As a result, it is possible to suppress an increase in the amount of current flowing in the anti-parallel diode of the switching element of the inverter 5 due to the increase in the impedance due to the wiring path.

With the above-described configuration, reignition by the discharge power supply 11 is performed while the high frequency AC power supply 2 is operating, and the diode bridge circuit 13 rectifies any phase of discharge current flowing from the resonance capacitor 72 into the inverter 5. be able to. In addition, it is possible to reduce the recovery loss of the anti-parallel diode of the switching element of the inverter 5 and to suppress the transient heat generation due to the recovery short circuit.
Therefore, the rise of the applied voltage of the high frequency alternating current power supply 2 can be effectively prevented.

  The present invention can freely combine each embodiment within the scope of the invention, and can appropriately modify or omit each embodiment.

  DESCRIPTION OF SYMBOLS 1 Ignition device for internal combustion engines, 2 high frequency alternating current power supply, 3 direct current voltage source, 4 input capacitors, 5 inverters, 51, 52, 53, 54 switching elements, 6 transformers, 61 transformer primary side windings, 62 transformer secondary Side winding, 7 resonance circuits, 71 resonance reactors, 72 resonance capacitors, 8 voltage detection means, 9 current detection means, 10 spark plugs, 11 discharge power sources, 12 control units, 13 diode bridge circuits, 131, 132, 133, 134 diode

Claims (5)

An ignition plug for igniting a combustible mixture in a combustion chamber of an internal combustion engine;
A discharge power source for applying a DC high voltage between the electrodes of the spark plug to generate a spark discharge between the electrodes;
A high frequency alternating current power supply for applying a high frequency voltage to the discharge path of the spark discharge to generate a high frequency plasma between the electrodes;
An ignition device for an internal combustion engine having
The high frequency alternating current power supply is
A DC voltage source,
An input capacitor,
Voltage detection means for detecting an applied voltage of the input capacitor;
An inverter having a plurality of switching elements and converting a DC voltage output from the DC voltage source into an AC voltage;
A transformer having a primary winding connected to the output end of the inverter;
A resonant circuit connected to the secondary side winding of the transformer, having at least one or more capacitors and a reactor, for resonating the alternating voltage output from the inverter;
A control unit that controls the on and off operation of the switching element that constitutes the inverter;
Equipped with
The control unit
The ignition operation is performed only by the discharge power source,
The inverter is operated to consume energy stored in the input capacitor as an energy consumption operation when the detected voltage of the input capacitor is higher than a preset threshold voltage. Engine igniter.   The control unit causes the switching element of the inverter to perform switching operation at a frequency higher than a resonance point formed by the stray capacitance of the resonance circuit and the spark plug, when performing the energy consumption operation. An ignition device for an internal combustion engine according to claim 1.   The control unit performs the switching of the inverter such that an alternating current voltage output from a secondary winding of the transformer is less than a discharge sustaining voltage of high frequency plasma discharge of the spark plug when performing the energy consumption operation. The ignition device for an internal combustion engine according to claim 1 or 2, wherein the duty ratio of on-pulse of the element is reduced.   The said high frequency alternating current power supply connects the diode bridge circuit between the said inverter and the said transformer, The ignition device for internal combustion engines of any one of the Claims 1-3 characterized by the above-mentioned.   5. The ignition device for an internal combustion engine according to claim 4, wherein the diode bridge circuit has a forward voltage smaller than that of a diode provided in the switching element of the inverter.

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